System simulation and graphical data flow programming in a common environment using wire data flow

ABSTRACT

Various embodiments of systems and methods are described in which system simulation techniques are combined with graphical programming techniques in a common environment. For example, various embodiments of the methods comprise displaying a graphical data flow diagram connected to a system diagram, e.g., where the graphical data flow diagram and the system diagram are displayed together in a compound diagram. In the displayed compound diagram, the graphical data flow diagram may be connected to the system diagram, e.g., by a line or wire. In one embodiment the wire may visually indicate that the graphical data flow diagram is executable to produce a value that is provided as an input signal for a simulation performed based on the system diagram. In another embodiment the wire may visually indicate that the graphical data flow diagram receives an output value from the system simulation as input.

FIELD OF THE INVENTION

The present invention relates to the field of graphical data flowprogramming. The present invention also relates to the field of systemsimulation, e.g., simulation of a system such as a circuit or otherphysical system. More particularly, the invention relates to a methodfor creating a diagram including a graphical data flow diagram portionand a system diagram portion, where the graphical data flow portion isexecutable to produce an input signal for a simulation performed basedon the system diagram and/or where the graphical data flow portionreceives an output value from the simulation as input.

DESCRIPTION OF THE RELATED ART

The present invention relates to the field of graphical data flowprogramming. Traditionally, high level text-based programming languageshave been used by programmers in writing application programs. Manydifferent high level text-based programming languages exist, includingBASIC, C, Java, FORTRAN, Pascal, COBOL, ADA, APL, etc. Programs writtenin these high level text-based languages are translated to the machinelanguage level by translators known as compilers or interpreters. Thehigh level text-based programming languages in this level, as well asthe assembly language level, are referred to herein as text-basedprogramming environments.

Increasingly, computers are required to be used and programmed by thosewho are not highly trained in computer programming techniques. Whentraditional text-based programming environments are used, the user'sprogramming skills and ability to interact with the computer systemoften become a limiting factor in the achievement of optimal utilizationof the computer system.

There are numerous subtle complexities which a user must master beforehe can efficiently program a computer system in a text-basedenvironment. The task of programming a computer system to model orimplement a process often is further complicated by the fact that asequence of mathematical formulas, steps or other procedures customarilyused to conceptually model a process often does not closely correspondto the traditional text-based programming techniques used to program acomputer system to model such a process. In other words, the requirementthat a user program in a text-based programming environment places alevel of abstraction between the user's conceptualization of thesolution and the implementation of a method that accomplishes thissolution in a computer program. Thus, a user often must substantiallymaster different skills in order to both conceptualize a problem orprocess and then to program a computer to implement a solution to theproblem or process. Since a user often is not fully proficient intechniques for programming a computer system in a text-based environmentto implement his solution, the efficiency with which the computer systemcan be utilized often is reduced.

To overcome the above shortcomings, various graphical programmingenvironments now exist which allow a user to construct a graphicalprogram or graphical diagram, also referred to as a block diagram. U.S.Pat. Nos. 4,901,221; 4,914,568; 5,291,587; 5,301,301; and 5,301,336;among others, to Kodosky et al disclose a graphical programmingenvironment which enables a user to easily and intuitively create agraphical program. Graphical programming environments such as thatdisclosed in Kodosky et al can be considered a higher and more intuitiveway in which to interact with a computer. A graphically basedprogramming environment can be represented at a level above text-basedhigh level programming languages such as C, Basic, Java, etc.

A user may assemble a graphical program by selecting various blocks oricons which represent desired functionality, and then connecting theblocks or icons together to create the graphical program. Thus the blockdiagram may include a plurality of interconnected blocks such that thediagram created graphically displays a procedure or method foraccomplishing a certain result, such as manipulating one or more inputvalues and/or producing one or more output values. In response to theuser constructing a block diagram or graphical program using the blockdiagram editor, data structures and/or program instructions may beautomatically constructed which characterize an execution procedure thatcorresponds to the displayed procedure. The graphical program may becompiled or interpreted by a computer.

A graphical program may have a graphical user interface. For example, increating a graphical program, a user may create a front panel or userinterface panel. The front panel may include various graphical userinterface elements or front panel objects, such as user interfacecontrols and/or indicators, that represent or display the respectiveinput and output that will be used by the graphical program, and mayinclude other icons which represent devices being controlled.

Thus, graphical programming has become a powerful tool available toprogrammers. Graphical programming environments such as the NationalInstruments LabVIEW product have become very popular. Tools such asLabVIEW have greatly increased the productivity of programmers, andincreasing numbers of programmers are using graphical programmingenvironments to develop their software applications. In particular,graphical programming tools are being used for applications such as testand measurement, data acquisition, process control, man machineinterface (MMI), supervisory control and data acquisition (SCADA)applications, modeling, image processing/machine vision applications,and motion control, among others.

The blocks in the block diagram of a graphical program may be connectedby lines or wires representing one or more of data flow, control flow,and/or execution flow. A graphical program in which the blocks areconnected primarily according to a data flow representation is referredto as a graphical data flow program. The block diagram for a graphicaldata flow program is also referred to as a graphical data flow diagram.Connections (e.g., lines or wires) between blocks in a graphical dataflow diagram visually indicate that data produced by one block is usedby another block. For example, a graphical data flow diagram may includea first block connected by a wire to a second block, where the wirevisually indicates that output data produced by the first block ispassed as input data to the second block.

The present invention also relates to the field of system simulation.Simulation of a system may be implemented using software, hardware, or acombination of both. Creating a system simulation typically involvescreating a model of the system, where the model represents the system orrepresents certain aspects of the system. For a given system, the systemmay be modeled in any number of different ways. Thus, the type of modelthat is created may depend on the particular aspects of the system thatthe modeler is interested in or the particular purpose of performing thesimulation.

Creating a model of a system generally involves simplifying orapproximating certain aspects of the system. For some systems orproblems, a simple, abstracted model may serve to solve the problem athand quite well, whereas for other systems or problems, a more complexmodel representing many details of the actual system may be desirable.

There are many reasons why it may be necessary or desirable to simulatea system. One common situation where simulation is useful is when thereal system has not yet been created. In this instance, the system maybe simulated in order to test design variations and predict whether theplanned system will operate as desired.

Any of various types of systems may be simulated. In general, a systemmodel may model physical, mechanical, electrical, chemical,thermodynamic, and/or other types of behavior of the system undersimulation. As a few illustrative examples, simulation may be performedfor systems such as an electronic circuit or other electronic system, anengine or engine component, an object in motion, a chemical reaction, apetroleum refining process, a room maintained at a setpoint temperature,a system of liquids flowing among different tanks, etc.

SUMMARY

Various embodiments of systems and methods are described in which systemsimulation techniques are combined with graphical programming techniquesin a common environment. For example, various embodiments of the methodscomprise displaying a graphical data flow diagram connected to a systemdiagram, e.g., where the graphical data flow diagram and the systemdiagram are displayed together in a common diagram (also referred toherein as a “compound diagram”). In the displayed compound diagram, thegraphical data flow diagram may be connected to the system diagram,e.g., by a line or wire. In one embodiment the wire may visuallyindicate that the graphical data flow diagram is executable to produce avalue that is provided as an input signal for a simulation performedbased on the system diagram. In another embodiment the wire may visuallyindicate that the graphical data flow diagram receives an output valuefrom the system simulation as input.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates a computer system operable to create, display, and/orrun a compound diagram, where the compound diagram includes a graphicaldata flow diagram connected to a system diagram;

FIG. 2 illustrates an embodiment in which the computer system couples toa Field Programmable Gate Array (FPGA) device;

FIG. 3 is a block diagram representing one embodiment of the computersystem in more detail;

FIG. 4 illustrates an exemplary instrumentation control system in whichthe computer system connects to one or more instruments;

FIG. 5 is a flowchart diagram illustrating one embodiment of a methodfor creating, displaying, and running a compound diagram, where thecompound diagram includes a graphical data flow diagram connected to acircuit diagram such that the graphical data flow diagram receives avalue computed by a simulation performed on the circuit diagram asinput;

FIG. 6 is a flowchart diagram illustrating an exemplary method forperforming a circuit simulation according to one embodiment;

FIGS. 7-9 illustrate an exemplary circuit diagram and graphical dataflow diagram connected to each other according to one embodiment of themethod of FIG. 5;

FIG. 10 is a flowchart diagram illustrating one embodiment of a methodfor creating, displaying, and running a compound diagram, where thecompound diagram includes a graphical data flow diagram connected to acircuit diagram such that the graphical data flow diagram executes toproduce output data that is provided as an input signal for a simulationperformed based on the circuit diagram;

FIGS. 11 and 12 illustrate an exemplary circuit diagram and graphicaldata flow diagram connected to each other according to one embodiment ofthe method of FIG. 10;

FIG. 13 illustrates an example in which the method of FIGS. 5 and 10 arecombined; and

FIGS. 14-20 illustrate several exemplary compound diagrams in whichcircuit diagrams are connected to graphical data flow diagrams.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Incorporation by Reference

The following references are hereby incorporated by reference in theirentirety as though fully and completely set forth herein:

U.S. Pat. No. 5,481,741 titled “Method and Apparatus for ProvidingAttribute Nodes in a Graphical Data Flow Environment”.

U.S. Pat. No. 6,173,438 titled “Embedded Graphical Programming System”filed Aug. 18, 1997.

U.S. Pat. No. 6,219,628 titled “System and Method for Configuring anInstrument to Perform Measurement Functions Utilizing Conversion ofGraphical Programs into Hardware Implementations,” filed Aug. 18, 1997.

U.S. Patent Application Publication No. 20010020291 (Ser. No.09/745,023) titled “System and Method for Programmatically Generating aGraphical Program in Response to Program Information,” filed Dec. 20,2000.

U.S. patent application Ser. No. 10/046,861 titled, “System and Methodfor Performing a Hardware in the Loop Simulation Using a Plurality ofGraphical Programs that Share a Single Graphical User Interface,” filedJan. 15, 2002.

U.S. patent application Ser. No. 10/892,829 titled, “A Graphical ProgramWhich Executes a Timed Loop,” filed Jul. 16, 2004.

U.S. patent application Ser. No. 11/203,816 titled, “CombinationStructure Nodes for a Graphical Program,” filed Aug. 15, 2005.

U.S. patent application Ser. No. 11/356,711 titled, “Solver forSimulating a System in Real Time on a Programmable Hardware Element,”filed Feb. 17, 2006.

Terms

The following is a glossary of terms used in the present application:

Memory Medium—Any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks 104, or tape device; a computer systemmemory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM,Rambus RAM, etc.; or a non-volatile memory such as a magnetic media,e.g., a hard drive, or optical storage. The memory medium may compriseother types of memory as well, or combinations thereof. In addition, thememory medium may be located in a first computer in which the programsare executed, or may be located in a second different computer whichconnects to the first computer over a network, such as the Internet. Inthe latter instance, the second computer may provide programinstructions to the first computer for execution. The term “memorymedium” may include two or more memory mediums which may reside indifferent locations, e.g., in different computers that are connectedover a network.

Carrier Medium—a memory medium as described above, as well as signalssuch as electrical, electromagnetic, or digital signals, conveyed via acommunication medium such as a bus, network and/or a wireless link.

Medium—includes one or more of a memory medium, carrier medium, and/orprogrammable hardware element; encompasses various types of mediums thatcan either store program instructions/data structures or can beconfigured with a hardware configuration program. For example, a mediumthat is “configured to perform a function or implement a softwareobject” may be 1) a memory medium or carrier medium that stores programinstructions, such that the program instructions are executable by aprocessor to perform the function or implement the software object; 2) amedium carrying signals that are involved with performing the functionor implementing the software object; and/or 3) a programmable hardwareelement configured with a hardware configuration program to perform thefunction or implement the software object.

Program—the term “program” is intended to have the full breadth of itsordinary meaning. The term “program” includes 1) a software programwhich may be stored in a memory and is executable by a processor or 2) ahardware configuration program useable for configuring a programmablehardware element.

Software Program—the term “software program” is intended to have thefull breadth of its ordinary meaning, and includes any type of programinstructions, code, script and/or data, or combinations thereof, thatmay be stored in a memory medium and executed by a processor. Exemplarysoftware programs include programs written in text-based programminglanguages, such as C, C++, Pascal, Fortran, Cobol, Java, assemblylanguage, etc.; graphical programs (programs written in graphicalprogramming languages); assembly language programs; programs that havebeen compiled to machine language; scripts; and other types ofexecutable software. A software program may comprise two or moresoftware programs that interoperate in some manner.

Hardware Configuration Program—a program, e.g., a bit file, that can beused to program or configure a programmable hardware element.

Graphical Program—A program comprising a plurality of interconnectedblocks or icons, wherein the plurality of interconnected blocks or iconsvisually indicate functionality of the program.

The following provides examples of various aspects of graphicalprograms. The following examples and discussion are not intended tolimit the above definition of graphical program, but rather provideexamples of what the term “graphical program” encompasses:

The blocks in a graphical program may be connected in one or more of adata flow, control flow, and/or execution flow format. The blocks mayalso be connected in a “signal flow” format, which is a subset of dataflow.

Exemplary graphical program development environments which may be usedto create graphical programs include LabVIEW, DasyLab, DiaDem andMatrixx/SystemBuild from National Instruments, Simulink from theMathWorks, VEE from Agilent, WiT from Coreco, Vision Program Managerfrom PPT Vision, SoftWIRE from Measurement Computing, Sanscript fromNorthwoods Software, Khoros from Khoral Research, SnapMaster from HEMData, Vis Sim from Visual Solutions, ObjectBench by SES (Scientific andEngineering Software), and VisiDAQ from Advantech, among others.

The term “graphical program” includes models or block diagrams createdin graphical modeling environments, wherein the model or block diagramcomprises interconnected blocks or icons that visually indicateoperation of the model or block diagram; exemplary graphical modelingenvironments include Simulink, SystemBuild, Vis Sim, Hypersignal BlockDiagram, etc.

A graphical program may be represented in the memory of the computersystem as data structures and/or program instructions. The graphicalprogram, e.g., these data structures and/or program instructions, may becompiled or interpreted to produce machine language that accomplishesthe desired method or process as shown in the graphical program.

Input data to a graphical program may be received from any of varioussources, such as from a device, unit under test, a process beingmeasured or controlled, another computer program, a database, or from afile. Also, a user may input data to a graphical program or virtualinstrument using a graphical user interface, e.g., a front panel.

A graphical program may optionally have a GUI associated with thegraphical program. In this case, the plurality of interconnected blocksare often referred to as the block diagram portion of the graphicalprogram.

Block—In the context of a graphical program, an element that may beincluded in a graphical program. A block may have an associated iconthat represents the block in the graphical program, as well asunderlying code or data that implements functionality of the block.Exemplary blocks include function blocks, sub-program blocks, terminalblocks, structure blocks, etc. Blocks may be connected together in agraphical program by connection icons or wires.

The blocks in a graphical program may also be referred to as graphicalprogram nodes or simply nodes (not to be confused with the nodes thatconnect components in a circuit diagram).

Graphical Data Flow Program (or Graphical Data Flow Diagram)—A graphicalprogram or diagram comprising a plurality of interconnected blocks,wherein at least a subset of the connections among the blocks visuallyindicate that data produced by one block is used by another block. ALabVIEW VI is one example of a graphical data flow program.

Graphical User Interface—this term is intended to have the full breadthof its ordinary meaning. The term “Graphical User Interface” is oftenabbreviated to “GUI”. A GUI may comprise only one or more input GUIelements, only one or more output GUI elements, or both input and outputGUI elements.

The following provides examples of various aspects of GUIs. Thefollowing examples and discussion are not intended to limit the ordinarymeaning of GUI, but rather provide examples of what the term “graphicaluser interface” encompasses:

A GUI may comprise a single window having one or more GUI Elements, ormay comprise a plurality of individual GUI Elements (or individualwindows each having one or more GUI Elements), wherein the individualGUI Elements or windows may optionally be tiled together.

A GUI may be associated with a graphical program. In this instance,various mechanisms may be used to connect GUI Elements in the GUI withblocks in the graphical program. For example, when Input Controls andOutput Indicators are created in the GUI, corresponding blocks (e.g.,terminals) may be automatically created in the graphical program orblock diagram. Alternatively, the user can place terminal blocks in theblock diagram which may cause the display of corresponding GUI Elementsfront panel objects in the GUI, either at edit time or later at runtime. As another example, the GUI may comprise GUI Elements embedded inthe block diagram portion of the graphical program.

Front Panel—A Graphical User Interface that includes input controls andoutput indicators, and which enables a user to interactively control ormanipulate the input being provided to a program, and view output of theprogram, while the program is executing.

A front panel is a type of GUI. A front panel may be associated with agraphical program as described above.

In an instrumentation application, the front panel can be analogized tothe front panel of an instrument. In an industrial automationapplication the front panel can be analogized to the MMI (Man MachineInterface) of a device. The user may adjust the controls on the frontpanel to affect the input and view the output on the respectiveindicators.

Graphical User Interface Element—an element of a graphical userinterface, such as for providing input or displaying output. Exemplarygraphical user interface elements comprise input controls and outputindicators

Input Control—a graphical user interface element for providing userinput to a program. Exemplary input controls comprise dials, knobs,sliders, input text boxes, etc.

Output Indicator—a graphical user interface element for displayingoutput from a program. Exemplary output indicators include charts,graphs, gauges, output text boxes, numeric displays, etc. An outputindicator is sometimes referred to as an “output control”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

Measurement Device—includes instruments, data acquisition devices, smartsensors, and any of various types of devices that are operable toacquire and/or store data. A measurement device may also optionally befurther operable to analyze or process the acquired or stored data.Examples of a measurement device include an instrument, such as atraditional stand-alone “box” instrument, a computer-based instrument(instrument on a card) or external instrument, a data acquisition card,a device external to a computer that operates similarly to a dataacquisition card, a smart sensor, one or more DAQ or measurement cardsor modules in a chassis, an image acquisition device, such as an imageacquisition (or machine vision) card (also called a video capture board)or smart camera, a motion control device, a robot having machine vision,and other similar types of devices. Exemplary “stand-alone” instrumentsinclude oscilloscopes, multimeters, signal analyzers, arbitrary waveformgenerators, spectroscopes, and similar measurement, test, or automationinstruments.

A measurement device may be further operable to perform controlfunctions, e.g., in response to analysis of the acquired or stored data.For example, the measurement device may send a control signal to anexternal system, such as a motion control system or to a sensor, inresponse to particular data. A measurement device may also be operableto perform automation functions, i.e., may receive and analyze data, andissue automation control signals in response.

Referring now to FIG. 1, a computer system 82 is illustrated. Thecomputer system 82 may be operable to execute software operable todisplay a diagram referred to herein as a “compound diagram,” where thecompound diagram includes both a graphical data flow diagram portion anda system diagram portion. The compound diagram may be displayed on adisplay device of the computer system 82, such as an LCD screen, CRTmonitor, or other display device.

The graphical data flow diagram may comprise a plurality ofinterconnected blocks that visually indicate a process, e.g., analgorithm or function. The graphical data flow diagram may be executableto perform the process, e.g., after being compiled or interpreted intoexecutable program instructions. The blocks in the graphical data flowdiagram may be interconnected by lines or wires that represent data flowamong the blocks. For example, the graphical data flow diagram mayinclude a first block connected by a wire to a second block, where thewire visually indicates that output data produced by execution of thefirst block is passed as input data to the second block.

The system diagram may comprise a diagram of a system, e.g., a physicalsystem. As one example, the system diagram may comprise a diagram of acircuit, e.g., an analog circuit or other electrical circuit. The systemdiagram may represent a model of the system and may be used to simulatethe system, possibly after first being converted into another format,e.g., one or more data structures or equations describing the system.For example, as described below, in some embodiments the system diagrammay be automatically converted into a set of mathematical equations thatrepresent the system, where the mathematical equations are used by asolver to perform a simulation of the system, such as a time domainsolver that performs a time domain simulation or a frequency domainsolver that performs a frequency domain simulation.

The system diagram may include a plurality of components, e.g., whereeach component represents a physical component of the system. The systemdiagram may also include lines or wires that interconnect thecomponents. However, the lines or wires in the system diagram may differfrom the lines or wires in the graphical data flow diagram in that thelines or wires in the system diagram do not directly represent data flowamong the system components. For example, the lines or wires in thesystem diagram may represent physical connections or other physicalrelationships between physical components in the system. For example, ina circuit diagram, a wire (node) may be displayed between a firstresistor component and a second resistor component, where the wirerepresents a physical connection between the resistors.

The system diagram may also differ from the graphical data flow diagramin that the system diagram does not directly represent an executableprogram process. For example, instead of being compiled or interpretedinto executable program instructions, the system diagram may be used byother program logic to perform a simulation of the system, possiblyafter being converted into data structures or equations that representthe system, as described above.

In the displayed compound diagram, the graphical data flow diagram maybe connected to the system diagram, e.g., by a line or wire. In oneembodiment the wire may visually indicate that the graphical data flowdiagram is executable to produce a value that is provided as an inputsignal for the simulation performed based on the system diagram. Inanother embodiment the wire may visually indicate that the graphicaldata flow diagram receives an output value from the system simulation asinput.

In some embodiments the compound diagram may include multiple graphicaldata flow diagrams. For example, the compound diagram may include afirst wire between a first graphical data flow diagram and the systemdiagram, where the first wire visually indicates that the firstgraphical data flow diagram is executable to produce a value that isprovided as an input signal for the simulation performed based on thesystem diagram. The compound diagram may also include a second wirebetween the system diagram and a second graphical data flow diagram,where the second wire visually indicates that the second graphical dataflow diagram receives an output value from the system simulation asinput.

Also, in some embodiments the compound diagram may include multiplesystem diagrams. For example, the compound diagram may include a firstwire between a first system diagram and the graphical data flow diagram,where the first wire visually indicates that the graphical data flowdiagram receives an output value from a first simulation performed onthe first system diagram. The compound diagram may also include a secondwire between the graphical data flow diagram and a second systemdiagram, where the second wire visually indicates that the graphicaldata flow diagram is executable to produce a value that is provided asan input signal for a second simulation performed on the second systemdiagram.

In some embodiments the software executed by the computer system 82 mayalso be operable to create the compound diagram, e.g., in response touser input. Exemplary methods for creating the compound diagram aredescribed below.

In some embodiments the software executed by the computer system 82 mayalso be operable to run the compound diagram. Running the compounddiagram may comprise executing the graphical data flow diagram andperforming a simulation based on the system diagram. In someembodiments, running the compound diagram may also comprise providing anoutput value of the graphical data flow diagram as an input signal forthe simulation, e.g., in embodiments where the compound diagram includesa connection visually indicating this behavior. In other embodiments,running the compound diagram may also comprise providing a valuecomputed by the simulation as an input value to the graphical data flowdiagram, e.g., in embodiments where the compound diagram includes aconnection visually indicating this behavior.

The functions described above of creating, displaying, and running acompound diagram that includes a graphical data flow diagram portionconnected to a system diagram portion may be implemented by one or moresoftware applications or programs collectively referred to herein as“diagramming software”. In one embodiment the diagramming software maycomprise a single software application, e.g., development environmentapplication, operable to create, display, and run the compound diagram.In other embodiments, two or more software applications may operatetogether to implement one or more of these functions. As one example,the compound diagram may be created and displayed in a firstapplication, and the first application may interface with a secondapplication in order to run the compound diagram, e.g., may interfacewith a simulation application that performs a simulation on the systemdiagram and/or may interface with a graphical program runtime enginethat executes the graphical data flow diagram. As another example, thegraphical data flow diagram may be created in a first application, thesystem diagram may be created in a second application, and the systemdiagram may be imported into the first application and displayedtogether with the graphical data flow diagram in a compound diagram.

Referring again to FIG. 1, the computer system 82 may include one ormore memory mediums that store the diagramming software. The memorymedium(s) may also store operating system software, as well as othersoftware for operation of the computer system. The memory medium(s) mayalso store a compound diagram created by the diagramming software, e.g.,may store one or more files or data structures representing the compounddiagram. The computer system 82 may also include one or more processorsthat execute the diagramming software and other software.

It is noted that in some embodiments, the functions described above ofcreating, displaying, and running a compound diagram may be performed bymultiple computer systems or computing devices. For example, in someembodiments the compound diagram may be created and displayed on a firstcomputer system 82A, and may then be transferred to another computersystem 82B that runs the compound diagram.

As another example, in some embodiments, multiple computer systems orcomputing devices may operate in conjunction with each other to run thecompound diagram. For example, in one embodiment a first computer system82A may execute the graphical data flow diagram, and another computersystem 82B may perform the simulation based on the system diagram. Thecomputer systems may communicate to exchange data, e.g., to provide dataproduced by execution of the graphical data flow diagram as an inputsignal for the simulation and/or to provide a simulation value computedby the simulation as input data to the graphical data flow diagram.

As another example, the computer system 82 may couple to a device thatincludes programmable hardware in order to run the compound diagram. Forexample, FIG. 2 illustrates an embodiment in which the computer system82 couples to a Field Programmable Gate Array (FPGA) device 200. In thisexample, the FPGA device 200 includes programmable hardware configuredto implement a generic time domain solver 206. The FPGA device 200 isalso configured to store a system model 208, e.g., where the systemmodel 208 is automatically generated by converting the system diagraminto data structures and/or equations that represent the system undersimulation. Thus, the computer system 82 may execute the graphical dataflow diagram, and the FPGA device 200 may perform the system simulation.In some embodiments, performing the system simulation on the FPGA device200 or other programmable hardware may enable the simulation to proceedfaster than if the simulation were performed in software executing onthe computer system 82. The computer system 82 may exchange data withthe FPGA device 200 to implement the connection(s) shown in the compounddiagram between the graphical data flow diagram and the system diagram,similarly as described above.

FIG. 3 is a block diagram representing one embodiment of the computersystem 82 in more detail. It is noted that any type of computer systemconfiguration or architecture can be used as desired, and FIG. 3illustrates a representative PC embodiment. It is also noted that thecomputer system 82 may be a general purpose computer system, a computerimplemented on a card installed in a chassis, or other types ofembodiments. Elements of a computer not necessary to understand thepresent description have been omitted for simplicity.

In the illustrated embodiment, the computer system 82 includes at leastone central processing unit or CPU (processor) 160 which is coupled to aprocessor or host bus 162. The CPU 160 may be any of various types,including an x86 processor, e.g., a Pentium class, a PowerPC processor,a CPU from the SPARC family of RISC processors, as well as others. Amemory medium, typically comprising RAM and referred to as main memory,166 is coupled to the host bus 162 by means of memory controller 164.The main memory 166 may store diagramming software such as describedabove with reference to FIG. 1.

The host bus 162 may be coupled to an expansion or input/output bus 170by means of a bus controller 168 or bus bridge logic. The expansion bus170 may be the PCI (Peripheral Component Interconnect) expansion bus,although other bus types can be used. The expansion bus 170 includesslots for various devices that couple to the computer system 82, such asa GPIB card 122 and a Data Acquisition (DAQ) card 114. In theillustrated embodiment, the computer system 82 further comprises a videodisplay subsystem 180 and hard drive 182 coupled to the expansion bus170.

In the illustrated embodiment, an FPGA device 200 is also coupled to thecomputer system 82. As discussed above, in some embodiments the FPGAdevice 200 may be configured to perform a simulation based on the systemdiagram portion of a compound diagram. In other embodiments, the FPGAdevice 200 may not be present (e.g., the simulation may be performed bythe diagramming software executing on the computer system 82 orexecuting on another computer system), or the FPGA device 200 may becoupled to the computer system 82 through techniques other than anexpansion bus, or the simulation may be performed on a device other thanthe FPGA device 200, e.g., a device that includes another type ofprogrammable hardware element.

FIG. 4 illustrates an exemplary instrumentation control system 100 inwhich a host computer 82 connects to one or more instruments. The hostcomputer 82 may comprise a CPU, a display screen, memory, and one ormore input devices such as a mouse or keyboard as shown. In someembodiments the computer 82 may execute the graphical data flow diagramportion of a compound diagram, where the graphical data flow diagram isoperable to communicate with one or more instruments such as shown inFIG. 4. For example, in some embodiments the graphical data flow diagrammay execute to communicate with the one or more instruments to analyze,measure or control a unit under test (UUT) or process 150.

In other embodiments, one or more instruments such as shown in FIG. 4may be utilized in the system simulation performed based on the systemdiagram. As one example, the system simulation may be performed by anFPGA device 200, as described above. One or more instruments may becoupled to the FPGA device 200, e.g., where the one or more instrumentsprovide input signals affecting the simulation to the FPGA device 200and/or receive output signals computed by the simulation from the FPGAdevice 200.

The one or more instruments may include a GPIB instrument 112 andassociated GPIB interface card 122, a data acquisition board 114 andassociated signal conditioning circuitry 124, a VXI instrument 116, aPXI instrument 118, a video device or camera 132 and associated imageacquisition (or machine vision) card 134, a motion control device 136and associated motion control interface card 138, and/or one or morecomputer based instrument cards 142, among other types of devices.

The GPIB instrument 112 may be coupled to the computer 82 via the GPIBinterface card 122 provided by the computer 82. In a similar manner, thevideo device 132 may be coupled to the computer 82 via the imageacquisition card 134, and the motion control device 136 may be coupledto the computer 82 through the motion control interface card 138. Thedata acquisition board 114 may be coupled to the computer 82, and mayinterface through signal conditioning circuitry 124 to the UUT. Thesignal conditioning circuitry 124 may comprise an SCXI (SignalConditioning eXtensions for Instrumentation) chassis comprising one ormore SCXI modules 126.

The GPIB card 122, the image acquisition card 134, the motion controlinterface card 138, and the DAQ card 114 are typically plugged in to anI/O slot in the computer 82, such as a PCI bus slot, a PC Card slot, oran ISA, EISA or MicroChannel bus slot provided by the computer 82.However, these cards 122, 134, 138 and 114 are shown external tocomputer 82 for illustrative purposes. These devices may also beconnected to the computer 82 through a serial bus or through othermeans.

The VXI chassis or instrument 116 may be coupled to the computer 82 viaa VXI bus, MXI bus, or other serial or parallel bus provided by thecomputer 82. The computer 82 may include VXI interface logic, such as aVXI, MXI or GPIB interface card (not shown), which interfaces to the VXIchassis 116. The PXI chassis or instrument may be coupled to thecomputer 82 through the computer's PCI bus.

A serial instrument (not shown) may also be coupled to the computer 82through a serial port, such as an RS-232 port, USB (Universal Serialbus) or IEEE 1394 or 1394.2 bus, provided by the computer 82. In typicalinstrumentation control systems an instrument will not be present ofeach interface type, and in fact many systems may only have one or moreinstruments of a single interface type, such as only GPIB instruments.

The instruments may be coupled to a unit under test (UUT) or process150, or may be coupled to receive field signals, typically generated bytransducers. The system 100 may be used in a data acquisition andcontrol application, in a test and measurement application, an imageprocessing or machine vision application, a process control application,a man-machine interface application, a simulation application, or ahardware-in-the-loop validation application.

In one embodiment, one or more of the various instruments illustrated inFIG. 4 may couple to the computer 82 over a network, such as theInternet, an Ethernet network, or other wired or wireless networkconnection.

FIG. 5 is a flowchart diagram illustrating one embodiment of a methodfor creating, displaying, and running a compound diagram, where thecompound diagram includes a graphical data flow diagram connected to asystem diagram such that the graphical data flow diagram receives avalue computed by a simulation performed on the system diagram as input.It is noted that FIG. 5 represents an exemplary embodiment of themethod, and various alternative embodiments are contemplated. The methodof FIG. 5 may be implemented by diagramming software executing on thecomputer system 82.

In various embodiments, the system diagram displayed in the compounddiagram may represent any of various kinds of systems. For example, insome embodiments the system diagram may represent a physical system thatincludes electrical, mechanical, chemical, thermodynamic, or other typesof physical components. In particular, in some embodiments the systemdiagram may represent a physical device. The flowchart of FIG. 5represents an embodiment in which the system diagram comprises a circuitdiagram, e.g., a diagram representing an analog circuit, digitalcircuit, or other electrical circuit.

In 301, the circuit diagram may be created in response to user input,where the circuit diagram represents a circuit to be simulated. Forexample, in some embodiments the user may arrange icons representingcomponents of the circuit within a window displayed on the displaydevice of the computer system 82 in order to create a visualrepresentation of the circuit. For example, the diagramming software mayprovide a graphical user interface enabling the user to select from alibrary of circuit components, such as transistors, resistors,capacitors, inductors, switches, voltage and current sources, etc., anddisplay the selected circuit components in the circuit diagram inresponse to user input. The graphical user interface may also enable theuser to create wires, also referred to as nodes, connecting the variouscircuit components. Thus, in some embodiments the user may create thecircuit diagram in a direct graphical manner, e.g., by directly creatinga visual representation of the circuit.

In other embodiments the user may create the circuit diagram in anindirect manner, e.g., by specifying lines of text in a circuitdescription language, where the lines of text describe the circuit, suchas the components in the circuit and how they are connected to eachother. The circuit diagram may be automatically generated based on thetext describing the circuit.

In yet other embodiments the user may interact with one or moregraphical user interface dialogs to select various options indicatingdesired features of the circuit, and the diagramming software may thenautomatically create a circuit diagram having the features selected bythe user.

In addition to specifying the components of the circuit and the nodesconnecting the components together, the user may also specify variousproperties or parameters of the components. For example, for a resistorcomponent, the user may specify the resistance value. As anotherexample, for a voltage source component, the user may specify thevoltage value. The component properties may be specified in variousways, such as by interacting with graphical user interface dialogs forconfiguring the property values for various circuit components,specifying the property values in a text language, or displayingproperty value icons representing the property values within the circuitdiagram and connecting the property value elements to the respectivecircuit component icons in the circuit diagram.

In some embodiments, creating the circuit diagram may also comprisespecifying an input signal to the circuit diagram. For example, thecircuit diagram may represent an analog circuit or other electricalcircuit operable that operates with an electrical signal as input. Invarious embodiments the diagramming software may allow the user tospecify the input signal for the circuit diagram in various ways, e.g.,by connecting an icon representing the input signal to a component orwire in the circuit diagram or interacting with a graphical userinterface dialog to configure the input signal. Also, in someembodiments the input signal may be provided as output from a graphicaldata flow diagram, as described below with reference to FIG. 10.

Referring again to FIG. 5, in 303 a graphical data flow diagram may becreated in response to user input. Creating the graphical data flowdiagram may comprise assembling and interconnecting a plurality ofblocks in the graphical data flow diagram in response to user input. Thegraphical data flow diagram may be displayed on the display device ofthe computer system 82.

For example, the user may create the graphical data flow diagram byselecting desired blocks from a palette or menu of available blocks andplacing or “dragging and dropping” the selected blocks into thegraphical data flow diagram. For example, the blocks included in thegraphical data flow diagram may include function blocks (e.g., blocksoperable to perform a particular function), sub-program blocks (e.g.,blocks that encapsulate another graphical data flow diagram), controlblocks (e.g., blocks operable to perform control flow functions such aslooping or case selections, also referred to as structure blocks orstructure nodes), etc.

The user may also interconnect the blocks in the graphical data flowdiagram in a desired fashion, e.g., by creating lines or wires among theblocks. In particular, the user may interconnect the blocks to visuallyindicate data flow among the blocks. For example, the user may utilize awiring tool or wiring function provided by the diagramming software todisplay a wire connecting an output terminal of a first block to aninput terminal of a second block, such that the wire visually indicatesthat the first block produces output data that is passed as input datato the second block.

Thus, the blocks in the graphical data flow diagram may beinterconnected in response to user input in order to visually indicatedesired functionality of the graphical data flow diagram. For example,the plurality of interconnected blocks may visually indicate a processor function performed by the graphical data flow diagram when thegraphical data flow diagram is executed. In various embodiments the usermay create a graphical data flow diagram operable to perform anyprocess, function, or algorithm.

The graphical data flow diagram may thus include a plurality of blocksthat execute according to data flow semantics during execution of thegraphical data flow diagram. For example, blocks in the graphical dataflow diagram may obey the following semantic principles: a) The order ofexecution of the blocks is not explicitly specified by the user; b) Theorder of execution of the blocks is implied by data interdependencies;c) A block in the graphical data flow diagram begins execution inresponse to all of its necessary inputs becoming available.

In some embodiments, the graphical data flow diagram may also includeone or more blocks that do not completely follow data flow semanticprinciples, e.g., blocks providing functionality or capabilities that donot adhere to data driven execution. These blocks may be referred to as“control flow blocks,” “structure blocks,” or “structure nodes”. Forexample, these blocks may support various types of control flow (orexecution flow), as opposed to data flow, such as iteration, looping,conditional branching, sequencing, event-driven execution, and othernon-data flow behavior.

As one example, the LabVIEW graphical programming environment includes aWhile Loop structure node, a For Loop structure node, a Sequencestructure node, and a Case structure node. In the While Loop structurenode, graphical code associated with the While Loop structure noderepeatedly executes for a plurality of iterations while a condition istrue. In the For Loop structure node, graphical code associated with theFor Loop structure node executes for a pre-determined number ofiterations set by the user. In the Sequence structure node, the user canspecify different portions of graphical code to execute according to adesired sequence, without regard to data flow principles. In the Casestructure node, different portions of graphical code may executedependent on a condition.

A graphical code portion, i.e., one or more of the blocks in thegraphical data flow diagram, may be associated with a structure node orcontrol flow block, typically in a visual fashion, to indicate that thisgraphical code portion is executed according to the control flowfunction performed by the structure node. In other words, execution ofthe blocks in the graphical code portion associated with the structurenode is controlled by the structure node, whereas execution of graphicalcode that is not associated with the structure node is not controlled bythe structure node, but instead follows normal data flow principles.

Execution of the graphical code portion associated with a structure nodeor control flow block may be controlled in any of various ways,depending on the control flow function performed by the structure node.It is noted that once the execution of the graphical code portionassociated with the structure node has begun, the graphical code portionmay execute according to data flow principles. For example, in the caseof a While Loop structure node, blocks in the graphical code portionassociated with the While Loop structure node may execute according todata flow principles during each iteration of the loop. However, theWhile Loop controls the overall execution of the graphical code portionand causes the iteration to occur, whereas iteration may not normallyoccur in a data flow program.

It is also noted that various structure nodes or control flow blocks mayobey data flow principles at their inputs and outputs. For example, astructure node or control flow block itself may be connected to otherblocks in the graphical data flow diagram according to a data flowformat. As one example, a function block may be connected to an inputterminal of a For Loop structure node, where the function block outputsan integer value used to specify the desired number of iterations forthe For Loop. As another example, output data produced by the graphicalcode portion associated with the For Loop may be passed as input toother blocks in the graphical data flow diagram.

In some embodiments the graphical data flow diagram may also include auser interface portion or front panel portion. Where the graphical dataflow diagram includes a user interface portion, the user may assemblethe user interface on the display, e.g., by arranging various userinterface elements on the display.

Although the creation of the graphical data flow diagram in 303 isdescribed above in terms of the user arranging and interconnectingblocks in the graphical data flow diagram as desired, in otherembodiments the graphical data flow diagram may be created in any ofvarious other ways. For example, in some embodiments the user mayinteract with one or more graphical user interface dialogs to selectvarious options indicating desired execution functionality, and thediagramming software may then automatically generate a graphical dataflow diagram operable to perform the functionality selected by the user.

Referring again to FIG. 5, the circuit diagram and the graphical dataflow diagram may be displayed together within a compound diagram, asillustrated in 305. For example, the compound diagram may be displayedon the display device of the computer system 82, where the compounddiagram includes both the circuit diagram and the graphical data flowdiagram. For example, the circuit diagram and the graphical data flowdiagram may be displayed together in a single graphical user interfacewindow.

In some embodiments, the user may create the circuit diagram and thegraphical data flow diagram using a common development environmentapplication. For example, the development environment application maydisplay a window in which the user creates both the circuit diagram andthe graphical data flow diagram, as described above with reference to301 and 303.

In another embodiment the user may create the circuit diagram and thegraphical data flow diagram separately from each other, e.g., inseparate windows or possibly using different software applications. Inthis embodiment the circuit diagram and the graphical data flow diagramare preferably displayed together in the compound diagram after beingseparately created. For example, after the user has created the circuitdiagram and the graphical data flow diagram, the user may then requestthe circuit diagram to be imported into the graphical data flow diagramso that it is displayed together with the graphical data flow diagram,or vice versa.

As indicated in 307, the method may further comprise displaying aconnection between the circuit diagram and the graphical data flowdiagram in response to user input. For example, the user may use awiring tool or wiring function to create a wire, line, or otherconnection icon connecting the circuit diagram to the graphical dataflow diagram. The connection may visually indicate that a firstsimulation value computed in response to a simulation performed on thecircuit diagram is passed as input to the graphical data flow diagram,as described below.

For example, the user may provide user input causing a first wire to bedisplayed, where the first wire connects a wire (node) in the circuitdiagram to an input terminal of a block in the graphical data flowdiagram. The first wire may visually indicate that a value associatedwith the circuit wire (e.g., a voltage value along the circuit wire orother electrical characteristic of the circuit wire) is computed by thesimulation and is passed as input to the block in the graphical dataflow diagram.

As another example, the user may provide user input causing a first wireto be displayed, where the first wire connects a component icon in thecircuit diagram to an input terminal of a block in the graphical dataflow diagram. The first wire may visually indicate that a valueassociated with the component (e.g., an electrical characteristic of thecomponent) is computed by the simulation and is passed as input to theblock in the graphical data flow diagram.

As discussed above, the circuit diagram represents a model of thecircuit and may be used to perform a simulation of the circuit, e.g., atime domain simulation or other simulation. In 309, the simulation ofthe circuit is performed. Performing the simulation of the circuit maycomprise computing various simulation values that characterize operationof the circuit, such as voltage and current values along the wires inthe circuit, or other simulation values that represent electricalcharacteristics of various components or wires in the circuit. Inparticular, the simulation may compute the first simulation value, i.e.,the simulation value that the connection created in 307 visuallyindicates as being passed as input to the graphical data flow diagram.For example, where the connection created in 307 connects a wire in thecircuit diagram to a block in the graphical data flow diagram,performing the simulation may comprise computing a voltage value for thewire in the circuit diagram.

The method may further comprise executing the graphical data flowdiagram, as indicated in 311. The first simulation value computed in thecircuit simulation may be passed as input to the graphical data flowdiagram. For example, where the connection created in 307 connects awire in the circuit diagram to an input terminal of a first block in thegraphical data flow diagram, a voltage value may for the circuit wiremay be computed by the simulation in 309 and passed as input data to thefirst block in the graphical data flow diagram in 311. Executing thegraphical data flow diagram may comprise executing the first block(e.g., executing program instructions corresponding to the first block),where the first block uses the first simulation value computed in thecircuit simulation as an input parameter.

In various embodiments the graphical data flow diagram may execute toperform any of various functions, processes, or algorithms, where thefirst simulation value received from the circuit simulation may be usedby the graphical data flow diagram in any of various ways. Examples ofseveral graphical data flow diagrams that use simulation values computedby circuit simulations are described below.

In further embodiments of the method of FIG. 5, the user may createmultiple connections between the circuit diagram and the graphical dataflow diagram. Each connection may visually indicate that a respectivesimulation value is computed by the circuit simulation and passed asinput to a respective block in the graphical data flow diagram. Forexample, the user may create a first connection from a first circuitwire or circuit component in the circuit diagram to a first block in thegraphical data flow diagram and a second connection from a secondcircuit wire or circuit component in the circuit diagram to a secondblock in the graphical data flow diagram. The first connection mayvisually indicate that a first simulation value associated with thefirst circuit wire or circuit component is computed by the circuitsimulation and passed as input to the first block in the graphical dataflow diagram, and the second connection may visually indicate that asecond simulation value associated with the second circuit wire orcircuit component is computed by the circuit simulation and passed asinput to the second block in the graphical data flow diagram.

As another example, the user may create multiple graphical data flowdiagrams and connect each graphical data flow diagram to the circuitdiagram such that blocks in each respective graphical data flow diagramreceive one or more simulation values computed by the circuit simulationas input parameter values.

In various embodiments, the simulation of the circuit in block 309 ofFIG. 5 may be performed in any of various ways. FIG. 6 is a flowchartdiagram illustrating an exemplary method for performing the circuitsimulation according to one embodiment. The method of FIG. 6 may beimplemented by diagramming software executing on the computer system 82.

In 331, the circuit diagram may be automatically analyzed to determinecomponents in the circuit and wires (nodes) connecting the components.For example, the diagramming software may programmatically examine oneor more data structures representing the circuit diagram to determinewhat components are in the circuit, how the components are connected toeach other, properties of the components, etc.

In 333, a netlist describing the circuit diagram may be automaticallygenerated. Generating the netlist may comprise generating one or moredata structures that characterize the circuit, e.g., where the datastructures specify what components are in the circuit, specify thecircuit wires that connect the components to each other, specifyproperties of the components, etc. The one or more data structuresrepresenting the netlist may be stored in memory of the computer system82.

In 335, a set of mathematical equations representing the circuit may beautomatically generated, based on the netlist. In 337, the simulation ofthe circuit may be performed based on the set of equations. For example,in one embodiment the set of equations generated in 335 may representtime domain response behavior of the circuit. Thus, in 337 performingthe simulation of the circuit may comprise a solver solving theequations to perform a time domain response simulation of the circuit.

The set of equations generated in 335 may be represented in any ofvarious ways. For example, in one embodiment the netlist may beautomatically converted into a set of matrix coefficients, where thematrix coefficients specify the set of equations. The matrixcoefficients may be stored as one or more data structures.

As described above, performing the simulation of the circuit maycomprise computing various simulation values that characterize operationof the circuit, such as voltage and current values along the wires inthe circuit, or other simulation values that represent electricalcharacteristics of various components or wires in the circuit. Inparticular, the simulation may compute the first simulation value, i.e.,the simulation value that the connection created in 307 visuallyindicates as being passed as input to the graphical data flow diagram.

As described above, in creating the circuit diagram, the user may alsospecify an input signal to the circuit. The simulation of the circuitmay utilize the input signal in computing the various simulation values.Thus, the simulation of the circuit may depend on both the circuititself (e.g., the components in the circuit, the properties of thecomponents, and the connections among the components) and the inputsignal. For example, in a time domain simulation the solver may utilizedata representing the input signal as parameters in solving theequations that represent the circuit, and/or the equations may begenerated based on the input signal as well as the netlist.

As discussed above, in some embodiments the circuit simulation may beperformed on an FPGA device 200 or other programmable hardware device.For example, the FPGA device 200 may be configured to implement ageneric time domain solver 206. The computer system 82 may communicatewith the FPGA device 200, e.g., to upload the set of matrix coefficientsto the FPGA device 200. The generic time domain solver 206 on the FPGAdevice 200 may perform a time domain response simulation of the circuitbased on the matrix coefficients.

In one embodiment where the circuit simulation is performed on the FPGAdevice 200, the graphical data flow diagram may execute on the computersystem 82. The computer system 82 may communicate with the FPGA device200 to receive the first simulation value computed by the circuitsimulation and pass the first simulation value to the graphical dataflow diagram. In another embodiment the graphical data flow diagram mayalso be performed on the FPGA device 200 together with the circuitsimulation, e.g., by automatically converting the graphical data flowdiagram into a hardware configuration program and configuring the FPGAdevice 200 with the hardware configuration program.

In another embodiment, the circuit simulation may be performed on thecomputer system 82, where the graphical data flow diagram is alsoexecuted on the computer system 82. In another embodiment the circuitsimulation may be performed on a different computer system to which thecomputer system 82 is coupled via a network.

FIGS. 7-9 illustrate an exemplary circuit diagram and graphical dataflow diagram connected to each other according to one embodiment of themethod of FIG. 5. FIG. 7 illustrates an exemplary circuit diagramcreated according to one embodiment of block 301. The circuit diagramincludes various icons representing components of the circuit, such asresistors, voltage source, ground, etc., and also includes wiresconnecting the circuit components together. The circuit diagram may bedisplayed on a display of the computer system 82.

FIG. 8 illustrates an exemplary graphical data flow diagram createdaccording to one embodiment of block 303. The graphical data flowdiagram may be displayed on a display of the computer system 82. Thegraphical data flow diagram includes various function blocks 600connected according to a data flow representation. Each function block600 is operable to perform a respective function when the graphical dataflow diagram is executed. In this example, wires connected to the leftside of a given function block 600 represent input to the functionblock, and wires connected to the right side of a given function block600 represent output from the function block. For example, the graphicaldata flow diagram illustrates a wire connected from an output terminalof function block 600A to an input terminal of function block 600B,which visually indicates that output from function block 600A is passedas input to function block 600B.

FIG. 9 illustrates an exemplary compound diagram in which the circuitdiagram of FIG. 7 is connected to the graphical data flow diagram ofFIG. 8. More particularly, a circuit wire 620 of the circuit diagram isconnected to an input terminal 624 of function block 600A in thegraphical data flow diagram by a data flow wire 622. The data flow wire622 visually indicates that a simulation value associated with thecircuit wire 620 (e.g., a voltage value along the circuit wire 620) iscomputed by the circuit simulation and passed as input to the functionblock 600A in the graphical data flow diagram. Thus, the data flow wire622 does not represent a wire in the circuit, but instead representsinput to the graphical data flow diagram.

In an actual display of a compound diagram such as shown in FIG. 9 on acomputer display screen, the wires of the circuit diagram may bevisually distinguished from the data flow wire 622 and other wires ofthe graphical data flow diagram in order to visually indicate to theuser that they are different types of wires, e.g., by displaying the twotypes of wires in different colors. For example, in some embodiments thewires of the graphical data flow diagram may represent data flowsemantics among the blocks in the graphical data flow diagram, whereasthe wires of the circuit diagram do not represent data flow semantics.Further, in some embodiments the wires of the circuit diagram mayrepresent physical connections among physical components in the circuit,whereas the blocks of the graphical data flow diagram may not representphysical components, and the wires of the graphical data flow diagrammay not represent physical connections.

Thus, when the compound diagram of FIG. 9 is run, the circuit simulationmay be performed, e.g., by automatically analyzing the circuit diagramto generate a netlist, generating a set of equations or matrixcoefficients based on the netlist, and performing the simulation basedon the set of equations or matrix coefficients. The simulation maycompute a voltage value along the circuit wire 620, and the voltagevalue may be passed as an input parameter to the function block 600A inthe graphical data flow diagram. When the input to the function block600A is ready, e.g., when the voltage value has been passed to thefunction block 600A, the function block 600A may execute. The functionblock 600A may produce an output value that is passed to the functionblocks 600B and 600C, which may in turn execute in response to receivingthe data from the function block 600A, and so on.

FIG. 10 is a flowchart diagram illustrating one embodiment of a methodfor creating, displaying, and running a compound diagram, where thecompound diagram includes a graphical data flow diagram connected to asystem diagram such that the graphical data flow diagram executes toproduce output data that is provided as an input signal for a simulationperformed based on the system diagram. It is noted that FIG. 10represents an exemplary embodiment of the method, and variousalternative embodiments are contemplated. The method of FIG. 10 may beimplemented by diagramming software executing on the computer system 82.

In 351, a circuit diagram may be created in response to user input,similarly as described above.

In 353, a graphical data flow diagram in response to user input,similarly as described above.

In 355, the circuit diagram and the graphical data flow diagram may bedisplayed together within a common diagram, similarly as describedabove.

In 357, a connection may be displayed between the graphical data flowdiagram and the circuit diagram in response to user input, wherein theconnection visually indicates that first output data of the graphicaldata flow diagram is passed as an input signal to the circuit diagram.For example, the user may use a wiring tool or wiring function to createa wire, line, or other connection icon connecting the graphical dataflow diagram to the circuit diagram.

For example, the user may provide user input causing a first wire to bedisplayed, where the first wire connects an output terminal of a blockin the graphical data flow diagram to a wire or component in the circuitdiagram. The first wire may visually indicate that data produced by theblock in the graphical data flow diagram is provided as an input signalto the circuit diagram. For example, the data produced by the block inthe graphical data flow diagram may represent voltage or otherelectrical characteristics of an input signal to the circuit.

In 339, the graphical data flow diagram may be executed. The graphicaldata flow diagram may execute to produce the first output data. Invarious embodiments the graphical data flow diagram may be operable toperform any function, process, or algorithm in order to produce outputdata useable as an input signal to the circuit.

In 361, the simulation of the may be performed circuit. As describedabove, the simulation of the circuit may depend on both the circuititself (e.g., the components in the circuit, the properties of thecomponents, and the connections among the components) and the inputsignal to the circuit. Thus, the simulation of the circuit may computedifferent simulation values for the circuit, depending on the inputsignal data received from the graphical data flow diagram.

FIGS. 11 and 12 illustrate an exemplary circuit diagram and graphicaldata flow diagram connected to each other according to one embodiment ofthe method of FIG. 10. FIG. 11 illustrates an exemplary graphical dataflow diagram created according to one embodiment of block 353. In thissimple example, the graphical data flow diagram includes a functionblock 600E connected to a function block 600F.

FIG. 12 illustrates the graphical data flow diagram of FIG. 11 connectedto the circuit diagram of FIG. 7. More particularly, an output terminalof the function block 600F is connected to an icon representing avoltage source in the circuit diagram. Thus, when the graphical dataflow diagram is executed, the function block 600F may produce outputdata that is used as a voltage value for the voltage source whenperforming the simulation of the circuit.

FIG. 13 illustrates an example in which the method of FIGS. 5 and 10 arecombined. A first graphical data flow diagram is connected to thecircuit diagram to visually indicate that output of the first graphicaldata flow diagram is provided as an input signal for the circuitsimulation, similarly as described above with reference to FIG. 12. Asecond graphical data flow diagram is connected to the circuit diagramto visually indicate that a simulation value computed by the circuitsimulation is passed as input to the second graphical data flow diagram,similarly as described above with reference to FIG. 9.

In further embodiments of the methods described above, a graphical dataflow diagram may execute to dynamically change or provide feedback to acircuit under simulation. The compound diagram may be run for aplurality of iterations or for a plurality of time steps. At eachiteration or time step, a simulation value for the circuit may becomputed by a simulation of the circuit, and the simulation value may bepassed to the graphical data flow diagram. The graphical data flowdiagram may perform a process or algorithm based on the simulation valueand may then dynamically change or provide feedback to the circuit,depending on results of the process or algorithm. Thus, in the nextiteration or time step, the behavior of the circuit or the circuititself may be changed from the previous iteration or time step. Thus,the circuit simulation and the graphical data flow diagram may operatetogether to form a type of feedback loop in which simulation valuescomputed by the circuit simulation influences execution of the graphicaldata flow diagram, and the execution of the graphical data flow diagraminfluences the circuit.

For example, in some embodiments the graphical data flow diagram may beoperable to automatically change the topology of the circuit undersimulation, e.g., by adding additional components to the circuit,removing components from the circuit, or changing how components in thecircuit are connected to each other. For example, the graphical dataflow diagram may execute an algorithm based on a voltage value computedby the circuit simulation, where the algorithm determines whether andhow the circuit should be changed. As one simple example, depending onresults of the algorithm, an additional resistor may be added to thecircuit.

As another example, the graphical data flow diagram may be operable toautomatically change properties of components in the circuit. Forexample, the graphical data flow diagram may execute an algorithm basedon a voltage value computed by the circuit simulation, where thealgorithm determines whether and how properties of components in thecircuit should be changed. As one simple example, depending on resultsof the algorithm, the resistance of a resistor in the circuit may beincreased or reduced.

In other embodiments the graphical data flow diagram may be operable todynamically change an input signal to the circuit under simulation. Forexample, the graphical data flow diagram may execute an algorithm basedon a voltage value computed by the circuit simulation, where thealgorithm determines whether and how the input signal should be changed.

In other embodiments the graphical data flow diagram may be operable todynamically change or provide feedback to the circuit based oninformation or events other than simulation values computed by thecircuit simulation. As one example, the graphical data flow diagram mayinclude a graphical user interface that is displayed on the display ofthe computer system 82 while the compound diagram is running. The usermay be able to interact with the graphical user interface in order tocause the graphical data flow diagram to dynamically change the circuitor change an input signal to the circuit.

In various embodiments, the ability to dynamically change or providefeedback to a circuit under simulation may have a plethora of benefits.For example, the user may interact with a graphical user interface inorder to dynamically change the circuit in various ways and observe theeffects on the circuit's operation. For example, the graphical data flowdiagram may receive various simulation values at each iteration or timestep of the circuit simulation and display the simulation values inoutput indicators on the graphical user interface. The graphical userinterface may also include input controls allowing the user to selectvarious options or set properties affecting the circuit. In response tothe user interacting with the input controls, the graphical data flowdiagram may dynamically change the circuit as described above. Changingthe circuit may cause the simulation values displayed in the outputindicators to change in subsequent iterations or time steps, thusenabling the user to see the effects of changing the circuit. This maybe useful, for example, for instructors demonstrating the effects ofvarious circuit changes to students or for helping circuit developersdesign a circuit more efficiently.

As other examples, the ability to dynamically change or provide feedbackto a circuit under simulation may be useful for applications such ashardware-in-the-loop simulations and rapid control prototypingsimulations.

In various embodiments, dynamically changing the circuit simulation orproviding feedback from the graphical data flow diagram to the circuitsimulation may be implemented in various ways. For example, in someembodiments the graphical data flow diagram may be operable to changethe circuit by automatically changing one or more data structures thatrepresent the circuit diagram. In subsequent iterations or time steps,the simulation of the circuit may be performed based on the changedcircuit diagram. For example, in response to the change to the circuitdiagram, a new netlist describing the changed circuit may beautomatically generated, and the netlist may be converted into updatedequations or data structures used in the subsequent iterations or timesteps of the circuit simulation. In other embodiments the graphical dataflow diagram may directly change the netlist describing the circuitinstead of changing the circuit diagram.

In some embodiments the circuit diagram may be displayed on a display ofthe computer system 82 while the compound diagram is running, and thediagramming software may be operable to update the displayed circuitdiagram in response to dynamic changes to the circuit diagram. Forexample, if the graphical data flow diagram executes to add anadditional resistor component to the circuit then the diagrammingsoftware may automatically display a changed circuit diagramillustrating the additional resistor.

In various embodiments the user may configure the graphical data flowdiagram to dynamically change or provide feedback to the circuit undersimulation in any of various ways. For example, in some embodiments theuser may create a wire or other graphical information connecting thegraphical data flow diagram to the circuit diagram, where the wirevisually indicates that the graphical data flow diagram providesfeedback to or dynamically changes the circuit under simulation. Thus,for example, a compound diagram may display a first connection from thecircuit diagram to the graphical data flow diagram, where the firstconnection visually indicates that a simulation value computed by asimulation of the circuit is passed as input data to the graphical dataflow diagram, and the compound diagram may also display a secondconnection from the graphical data flow diagram to the circuit diagram,where the second connection visually indicates that the graphical dataflow diagram dynamically changes or provides feedback to the circuitunder simulation.

In other embodiments the graphical data flow diagram may be configuredto set a global variable or change data structures representing thecircuit under simulation, without necessarily visually displaying aconnection indicating feedback from the graphical data flow diagram tothe circuit.

FIGS. 14-20 illustrate several examples of compound diagrams such asdescribed above. For example, FIG. 14 illustrates an example in which acircuit diagram is connected to graphical data flow diagram blocks 800Aand 800B. The graphical data flow diagram blocks 800A execute to producedata that is provided as input signal to a circuit simulation performedon the circuit diagram. The circuit simulation produces a simulationvalue that is passed as input to the graphical data flow diagram blocks800B. In this simple example the graphical data flow diagram blocks 800Bsimply display the simulation value in a waveform chart indicator on agraphical user interface.

FIG. 15 illustrates an example similar to the example of FIG. 14.However, in this example, the circuit diagram and the graphical dataflow diagrams are displayed within a loop structure 820. The loopstructure 820 indicates that the circuit is simulated and the graphicaldata flow diagrams are executed for a plurality of iterations or timesteps. FIG. 15 also illustrates a connection from the block 800C labeled“User algorit.” to the circuit diagram. The block 800C may represent anarbitrarily complex algorithm that uses the simulation value receivedfrom the circuit simulation as input. For example, the block 800C mayencapsulate a more complex graphical data flow diagram (or may bereplaced within the diagram of FIG. 15 with a more complex graphicaldata flow diagram). In this example, the output terminal of the block800C is connected to an inductor component icon in the circuit diagram.Thus, for example, the algorithm implemented by the graphical data flowdiagram may execute to dynamically change the inductance of the inductorcomponent depending on the simulation value passed as input to thealgorithm.

FIG. 16 illustrates an example of adaptive processing in whichresistance of the resistor 825 in the circuit is dynamically changedaccording to the level of a simulation value computed by the circuitsimulation. The load resistance value is decreased when the outputsignal level increases. The shown example acts like a compressor.

In some embodiments, graphical programming blocks may be incorporatedwithin a circuit diagram. For example, FIG. 17 illustrates an example inwhich a graphical program select block 835 is included in the circuitdiagram. The select block 835 does not represent a component of thecircuit per se, but instead affects a simulation value computed by thesimulation of the circuit. In this example, two circuit wires 837A and837B are connected to the left side of the select block 835. The selectblock 835 may also be configured with a threshold value in response touser input. When the circuit simulation is performed, the simulationoutput values (e.g., voltages) computed for the circuit wires 837A and837B may be compared to the threshold value specified for the block 835.The simulation output value (e.g., voltage) computed for the circuitwire 837C connected to the output terminal of the block 835 depends onwhether the simulation values for the circuit wires 837A and 837B exceedthe threshold value. In the shown example, the simulation output ischanged from a lower order low-pass filter to a higher order low-passfilter when the output signal gets too large.

FIG. 18 illustrates another example in which a graphical program blockis included in a circuit diagram. In this case, a case structure block840 is included in the circuit diagram. The block 800E computes aBoolean value and passes the Boolean value to the case structure block840. If the value is True, then the case structure frame shown in FIG.18 is selected. If the value is False, then the case structure frameshown in FIG. 19 is selected. As shown, the case structure frame in FIG.18 includes extra circuit components compared to the case structureframe in FIG. 19. Thus, the case structure block 840 is operable todynamically change the topology of the circuit, depending on feedbackfrom the block 800E, where the feedback from the block 800E in turndepends on simulation values computed by the circuit simulation. In thisexample, the order of a low-pass filter is increased when a signal levelbecomes lager than a user defined threshold value configured for theblock 800E.

FIG. 20 illustrates an adaptive monitoring example in which a singlesignal is used to monitor a simulation result, and depending on themonitored values, the simulation of more signals may or may not beinstantiated. This can be used, for example, to speed up a simulation byalways performing a ‘coarse’ monitoring simulation and only perform the‘fine’ simulation when specific conditions in the coarse simulationresult are present.

Thus, various embodiments of the methods described above may be employedin order to implement a development environment in which circuitsimulation techniques are combined with graphical programming techniquesin a common environment.

It is noted that FIGS. 14-20 illustrate particular embodiments ofdiagrams created according to the methods described above and are notintended to limit the scope of the methods. Numerous alternativeembodiments of compound diagrams including both circuit diagrams andgraphical data flow diagrams are contemplated.

As described above, in various embodiments, a graphical data flowdiagram may be combined with any of various kinds of system diagramsother than circuit diagrams. Thus, methods similar to those describedabove may be utilized to integrate graphical data flow programmingtechniques with simulations performed to model any of various kinds ofsystems, such as mechanical, chemical, or neural systems, to name a fewexamples. Furthermore, any of various techniques may be used insimulating the systems, such as time domain response simulationstechniques, frequency domain response simulation techniques, etc.

It is noted that various embodiments may further include receiving,sending, or storing instructions and/or data implemented in accordancewith the foregoing description upon a computer-readable memory medium.Generally speaking, a computer-readable memory medium may includestorage media or memory media such as magnetic or optical media, e.g.,disk or CD-ROM, volatile or non-volatile media such as RAM (e.g. SDRAM,DDR SDRAM, RDRAM, SRAM, etc.), ROM, etc. for storing programinstructions. Such a computer-readable memory medium may store programinstructions received from or sent on any transmission media or signalssuch as electrical, electromagnetic, or digital signals, conveyed via acommunication medium such as network and/or a wireless link.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

1. A computer-implemented method for simulating a circuit, the methodcomprising: displaying on a display a circuit diagram, wherein thecircuit diagram represents the circuit, wherein the circuit diagramcomprises a plurality of components interconnected by wires, wherein thewires interconnecting the plurality of components in the circuit diagramcomprise wires of a first type, and wherein the wires of the first typedo not represent data flow semantics among the components in the circuitdiagram; displaying on the display a graphical data flow diagramconnected to the circuit diagram, wherein the graphical data flowdiagram comprises a plurality of interconnected blocks that visuallyindicate functionality of the graphical data flow diagram, wherein theblocks in the graphical data flow diagram are interconnected by wires ofa second type, and wherein the wires of the second type represent dataflow semantics among the blocks in the graphical data flow diagram;performing a simulation of the circuit; and executing the graphical dataflow diagram, wherein said executing the graphical data flow diagramcomprises one or more of: passing a first simulation value computed bythe simulation of the circuit as input to the graphical data flowdiagram; or producing output data, wherein the output data is providedas an input signal for the simulation of the circuit.
 2. The method ofclaim 1, wherein the wires between the blocks in the graphical data flowdiagram visually indicate that data produced by one block is used byanother block.
 3. The method of claim 1, wherein said displaying thegraphical data flow diagram connected to the circuit diagram comprisesdisplaying a first wire from the circuit diagram to a first block in thegraphical data flow diagram, wherein the first wire visually indicatesthat the first simulation value computed by the simulation of thecircuit is passed as input to the first block in the graphical data flowdiagram; wherein said passing the first simulation value to thegraphical data flow diagram comprises passing the first simulation valueto the first block in the graphical data flow diagram.
 4. The method ofclaim 1, wherein said displaying the graphical data flow diagramconnected to the circuit diagram comprises displaying a first wire froma first block in the graphical data flow diagram to the circuit diagram,wherein the first wire visually indicates that the output data producedby executing the first block in the graphical data flow diagram isprovided as the input signal for the simulation of the circuit.
 5. Themethod of claim 1, wherein said performing the simulation of the circuitcomprises computing the first simulation value, wherein the firstsimulation value is passed as input to the graphical data flow diagram;wherein the graphical data flow diagram executes to perform one or moreof: displaying the first simulation value; analyzing the firstsimulation value; or performing an algorithm based on the firstsimulation value.
 6. The method of claim 1, wherein said performing thesimulation of the circuit comprises: automatically generating a netlistbased on the circuit diagram; and performing the simulation of thecircuit based on the netlist.
 7. The method of claim 1, wherein thewires of the first type have a first appearance, and wherein the wiresof the second type have a second appearance to visually distinguish thewires of the first type from the wires of the second type.
 8. The methodof claim 1, wherein the wires of the first type represent physicalconnections among components in the circuit; wherein the wires of thesecond type do not represent physical connections.
 9. The method ofclaim 1, wherein said executing the graphical data flow diagram providesfeedback to the simulation of the circuit.
 10. The method of claim 1,wherein said executing the graphical data flow diagram further comprisesmodifying the circuit.
 11. The method of claim 10, wherein saidmodifying the circuit comprises changing a component of the circuit. 12.The method of claim 10, wherein said modifying the circuit compriseschanging a topology of the circuit.
 13. The method of claim 10, whereinsaid modifying the circuit comprises adding a component to the circuit.14. The method of claim 1, further comprising: creating the circuitdiagram in response to user input.
 15. The method of claim 1, furthercomprising: creating the graphical data flow diagram in response to userinput.
 16. A computer-readable memory medium for simulating a circuit,the memory medium comprising program instructions executable to: displayon a display a circuit diagram, wherein the circuit diagram representsthe circuit, wherein the circuit diagram comprises a plurality ofcomponents interconnected by wires, wherein the wires interconnectingthe plurality of components in the circuit diagram comprise wires of afirst type, and wherein the wires of the first type do not representdata flow semantics among the components in the circuit diagram; displayon the display a graphical data flow diagram connected to the circuitdiagram, wherein the graphical data flow diagram comprises a pluralityof interconnected blocks that visually indicate functionality of thegraphical data flow diagram, wherein the blocks in the graphical dataflow diagram are interconnected by wires of a second type, and whereinthe wires of the second type represent data flow semantics among theblocks in the graphical data flow diagram; perform a simulation of thecircuit; and execute the graphical data flow diagram, wherein saidexecuting the graphical data flow diagram comprises one or more of:passing a first simulation value computed by the simulation of thecircuit as input to the graphical data flow diagram; or producing outputdata, wherein the output data is provided as an input signal for thesimulation of the circuit.
 17. The memory medium of claim 16, whereinsaid displaying the graphical data flow diagram connected to the circuitdiagram comprises displaying a first wire from the circuit diagram to afirst block in the graphical data flow diagram, wherein the first wirevisually indicates that the first simulation value computed by thesimulation of the circuit is passed as input to the first block in thegraphical data flow diagram; wherein said passing the first simulationvalue to the graphical data flow diagram comprises passing the firstsimulation value to the first block in the graphical data flow diagram.18. The memory medium of claim 16, wherein said displaying the graphicaldata flow diagram connected to the circuit diagram comprises displayinga first wire from a first block in the graphical data flow diagram tothe circuit diagram, wherein the first wire visually indicates that theoutput data produced by executing the first block in the graphical dataflow diagram is provided as the input signal for the simulation of thecircuit.
 19. The memory medium of claim 16, wherein said performing thesimulation of the circuit comprises computing the first simulationvalue, wherein the first simulation value is passed as input to thegraphical data flow diagram; wherein the graphical data flow diagramexecutes to perform one or more of: displaying the first simulationvalue; analyzing the first simulation value; or performing an algorithmbased on the first simulation value.
 20. The memory medium of claim 16,wherein said performing the simulation of the circuit comprises:automatically generating a netlist based on the circuit diagram; andperforming the simulation of the circuit based on the netlist.
 21. Thememory medium of claim 16, wherein the wires of the first type have afirst appearance, and wherein the wires of the second type have a secondappearance to visually distinguish the wires of the first type from thewires of the second type.
 22. The memory medium of claim 16, wherein thewires of the first type represent physical connections among componentsin the circuit; wherein the wires of the second type do not representphysical connections.
 23. The memory medium of claim 16, wherein saidexecuting the graphical data flow diagram further comprises modifyingthe circuit.
 24. The memory medium of claim 23, wherein said modifyingthe circuit comprises changing a component of the circuit.
 25. Thememory medium of claim 23, wherein said modifying the circuit compriseschanging a topology of the circuit.
 26. The memory medium of claim 23,wherein said modifying the circuit comprises adding a component to thecircuit.
 27. The memory medium of claim 16, wherein the programinstructions are further executable to: create the circuit diagram inresponse to user input.
 28. The memory medium of claim 16, wherein theprogram instructions are further executable to: create the graphicaldata flow diagram in response to user input.
 29. A computer-implementedmethod for simulating a system, the method comprising: displaying on adisplay a circuit diagram in response to user input, wherein the circuitdiagram comprises a plurality of components connected by wires, whereinthe wires interconnecting the plurality of components in the circuitdiagram comprise wires of a first type, and wherein the wires of thefirst type represent physical connections among components in thecircuit; displaying on the display a graphical data flow diagramconnected to the circuit diagram in response to user input, wherein thegraphical data flow diagram comprises a plurality of interconnectedblocks that visually indicate functionality of the graphical data flowdiagram, wherein the blocks in the graphical data flow diagram areinterconnected by wires of a second type, and wherein the wires of thesecond type represent data flow semantics among the blocks in thegraphical data flow diagram; simulating the circuit, wherein saidsimulating comprises computing at least one simulation value; andexecuting the graphical data flow diagram, wherein said executingcomprises modifying at least a portion of the circuit based on the atleast one simulation value.
 30. A computer-implemented method forsimulating a system, the method comprising: displaying on a display acircuit diagram in response to user input, wherein the circuit diagramcomprises a plurality of components connected by wires, wherein thewires interconnecting the plurality of components in the circuit diagramcomprise wires of a first type, and wherein the wires of the first typerepresent physical connections among components in the circuit;displaying on the display a graphical data flow diagram connected to thecircuit diagram in response to user input, wherein the graphical dataflow diagram comprises a plurality of interconnected blocks thatvisually indicate functionality of the graphical data flow diagram,wherein the blocks in the graphical data flow diagram are interconnectedby wires of a second type, and wherein the wires of the second type donot represent physical connections; simulating the circuit, wherein saidsimulating comprises computing at least one simulation value; andexecuting the graphical data flow diagram, wherein said executingcomprises analyzing the at least one simulation value.
 31. The method ofclaim 30, wherein said displaying the graphical data flow diagramconnected to the circuit diagram comprises displaying a first wire fromthe circuit diagram to a first block in the graphical data flow diagram,wherein the first wire visually indicates that the at least onesimulation value computed by the simulation of the circuit is passed asinput to the first block in the graphical data flow diagram.
 32. Themethod of claim 30, wherein said displaying the graphical data flowdiagram connected to the circuit diagram comprises displaying a firstwire from a first block in the graphical data flow diagram to thecircuit diagram, wherein the first wire visually indicates that outputdata produced by executing the first block in the graphical data flowdiagram is provided as an input signal for said simulating the circuit.33. The method of claim 30, wherein said simulating the circuitcomprises: automatically generating a netlist based on the circuitdiagram; and performing the simulation of the circuit based on thenetlist.
 34. The method of claim 30, wherein the wires of the first typehave a first appearance, and wherein the wires of the second type have asecond appearance to visually distinguish the wires of the first typefrom the wires of the second type.
 35. The method of claim 30, whereinsaid executing the graphical data flow diagram provides feedback forsaid simulating the circuit.
 36. The method of claim 30, wherein saidexecuting the graphical data flow diagram further comprises modifyingthe circuit.
 37. A computer accessible memory medium storing programinstructions executable for simulating a circuit, wherein the programinstructions are executable by a processor to: display on a display acircuit diagram in response to user input, wherein the circuit diagramcomprises a plurality of components connected by wires, wherein thewires interconnecting the plurality of components in the circuit diagramcomprise wires of a first type, and wherein the wires of the first typerepresent physical connections among components in the circuit; displayon the display a graphical data flow diagram connected to the circuitdiagram in response to user input, wherein the graphical data flowdiagram comprises a plurality of interconnected blocks that visuallyindicate functionality of the graphical data flow diagram, wherein theblocks in the graphical data flow diagram are interconnected by wires ofa second type, and wherein the wires of the second type do not representphysical connections; simulate the circuit, wherein said simulatingcomprises computing at least one simulation value; and execute thegraphical data flow diagram, wherein said executing comprises analyzingthe at least one simulation value.
 38. The memory medium of claim 37,wherein said displaying the graphical data flow diagram connected to thecircuit diagram comprises displaying a first wire from the circuitdiagram to a first block in the graphical data flow diagram, wherein thefirst wire visually indicates that the at least one simulation valuecomputed by the simulation of the circuit is passed as input to thefirst block in the graphical data flow diagram.
 39. The memory medium ofclaim 37, wherein said displaying the graphical data flow diagramconnected to the circuit diagram comprises displaying a first wire froma first block in the graphical data flow diagram to the circuit diagram,wherein the first wire visually indicates that output data produced byexecuting the first block in the graphical data flow diagram is providedas an input signal for said simulating the circuit.
 40. The memorymedium of claim 37, wherein said simulating the circuit comprises:automatically generating a netlist based on the circuit diagram; andperforming the simulation of the circuit based on the netlist.
 41. Thememory medium of claim 37, wherein the wires of the first type have afirst appearance, and wherein the wires of the second type have a secondappearance to visually distinguish the wires of the first type from thewires of the second type.
 42. The memory medium of claim 37, whereinsaid executing the graphical data flow diagram provides feedback forsaid simulating the circuit.
 43. The memory medium of claim 37, whereinsaid executing the graphical data flow diagram further comprisesmodifying the circuit.
 44. A computer accessible memory medium storingprogram instructions executable for simulating a circuit, wherein theprogram instructions are executable by a processor to: display on adisplay a circuit diagram in response to user input, wherein the circuitdiagram comprises a plurality of interconnected components, wherein theconnections interconnecting the plurality of components in the circuitdiagram comprise connections of a first type, and wherein theconnections of the first type represent physical connections amongcomponents in the circuit; display on the display a graphical data flowdiagram connected to the circuit diagram in response to user input,wherein the graphical data flow diagram comprises a plurality ofinterconnected blocks that visually indicate functionality of thegraphical data flow diagram, wherein the blocks in the graphical dataflow diagram are interconnected by connections of a second type, andwherein the connections of the second type represent data flow semanticsamong the blocks in the graphical data flow diagram; simulate thecircuit, wherein said simulating comprises computing at least onesimulation value; and execute the graphical data flow diagram, whereinsaid executing comprises analyzing the at least one simulation value.45. The memory medium of claim 44, wherein said displaying the graphicaldata flow diagram connected to the circuit diagram comprises displayinga first connection from the circuit diagram to a first block in thegraphical data flow diagram, wherein the first connection visuallyindicates that the first simulation value computed by the simulation ofthe circuit is passed as input to the first block in the graphical dataflow diagram.
 46. The memory medium of claim 44, wherein said displayingthe graphical data flow diagram connected to the circuit diagramcomprises displaying a first connection from a first block in thegraphical data flow diagram to the circuit diagram, wherein the firstconnection visually indicates that output data produced by executing thefirst block in the graphical data flow diagram is provided as an inputsignal for said simulating the circuit.
 47. The memory medium of claim44, wherein said simulating the circuit comprises: automaticallygenerating a netlist based on the circuit diagram; and performing thesimulation of the circuit based on the netlist.
 48. The memory medium ofclaim 44, wherein the connections of the first type have a firstappearance, and wherein the connections of the second type have a secondappearance to visually distinguish the connections of the first typefrom the connections of the second type.
 49. The memory medium of claim44, wherein said executing the graphical data flow diagram providesfeedback for said simulating the circuit.
 50. The memory medium of claim44, wherein said executing the graphical data flow diagram furthercomprises modifying the circuit.